Field of the Invention
The present invention relates to a process control device, a process control system, and a process control method.
Priority is claimed on Japanese Patent Application No. 2012-149352, filed Jul. 3, 2012, the content of which is incorporated herein by reference.
Description of the Related Art
Conventionally, process control systems that control various quantities of states (such as the pressure, the temperature, the flow amount, or the like) for industrial processes performed in plants have been established, and sophisticated automatic operations have been implemented. As shown in, for example, FIG. 7 of Japanese Patent No. 4399773 (hereinafter, “Patent Document 1”), FIG. 1 of International Publication No. 2005/050336 (hereinafter, “Patent Document 2”), and FIG. 1 of United States Patent Application Publication No. US 2007/0078980 (hereinafter, “Patent Document 3”), process control systems of the related art have a configuration such that multiple sensors such as a flowmeter and a thermometer, and an actuator are coupled directly to a controller. The controller controls the actuator in accordance with results of the detection by the sensors, thereby controlling the above various quantities of states.
Here, plants are often designed to have an approximately 30-year lifetime. On the other hand, various devices constituting a process control system (such as the above controller, the sensors, and the actuator) are constituted of versatile electronic components in many cases. For this reason, the lifetimes of the devices depend on the lifetimes of the electronic components, and are therefore approximately 10 years. A sensor alone can be exchanged when the lifetime thereof expires. However, versatile electronic components are mounted on an I/O card that is an interface of the controller, thereby limiting the lifetime of the controller to approximately 10 years, and also limiting the lifetime of the process control system.
Thus, various devices constituting the process control system have shorter lifetimes than the plant. Therefore, it is necessary to replace the process control system before the lifetime of the plant expires. For this reason, as shown in FIG. 1 of Patent Document 1, FIG. 2 of Patent Document 2, and FIG. 2 of Patent Document 3, it is conceivable to make a configuration such that various devices constituting a process control system are connected to the same network, and the above I/O card is removed, thereby extending the lifetime of the process control system.
Regarding various devices constituting a process control system, versatile electronic components are used for other parts than the I/O card of the controller. Additionally, recently, an allowable period for providing software used for the process control system, such as operating systems (OS) and application programs, has been becoming shorter to approximately 5 to 10 years. For this reason, as explained above, even if the lifetime of the process control system is extended as a result of removing the I/O card, it is eventually necessary to replace the process control system from the view points of both software and hardware.
Further, recently, there has been increasing demands for not only mainlining the functions of process control systems, but also aggressively enhancing the functions thereof, for various purposes (such as to save energy, to comply with environmental regulations, or to enhance the production efficiency). To meet such demands, it is necessary to replace the process control system already established in a plant with a new process control system before the lifetime of the plant expires.
Here, when a process control system is replaced, it is preferable to employ a reliable and safe replacement procedure such that controllability before and after the replacement is ensured, and thereafter enhancement of the existing functions or installment of new functions is performed. For this reason, it is necessary to ensure that the controllability of the process control system before the replacement is maintained even after the replacement. For this reason, when a process control system is replaced, it is necessary to make sufficient evaluation of the controllability of the process control system after the replacement, thereby requiring a long time and a large cost for the evaluation.
Regarding the replacement of the process control system, it is conceivable to temporarily make the existing system and the new system co-exist to evaluate the controllability of each system, and remove the existing system after the evaluation, thereby reducing the evaluating time. In the case where the existing and new systems co-exist, however, it is necessary to manage various devices used for each system (such as controllers) by different tag names, thereby causing difficulty with operation after the removal of the existing system.